In the display technology field, the flat panel display technologies, LCD (Liquid Crystal Display) and OLED (Organic Light Emitting Diode) have been gradually replaced the CRT (Cathode Ray Tube) displays. The flat light source technology is a new type light source and its skill development has been reached up for the mass production level of the market. In the flat panel display and flat light source technologies, the attachment of two sheet glasses is a very important skill. The package result directly influences the performance of the elements.
The ultra-violet light curing technology is the most earliest and most common skill employed for the LCD/OLED packages. It possesses properties below: no solvent or little solvent is required, which diminishes the pollution of the solvent to the environment; the energy consumption is less and low temperature curing is possible which is suitable for heat sensitive material; the curing speed is fast and efficiency is high which can be applied to the high speed production line. The occupied space of the curing apparatus is small. Nevertheless, the UV glue is organic material. The molecular clearance after curing becomes larger. The water vapor and the oxygen can easily pass through the media and reach to the inside of the sealed space. Therefore, the technology should be suitable for the application field which is not sensitive to the water vapor and the oxygen, such as LCD. The OLED elements are highly sensitive to the water vapor and the oxygen. When the UV package is applied, dryer can be generally arranged inside the elements to eliminate the water vapor passing through the media and reach the inside of the sealed space for extending the usage lifetime of the OLED elements.
The main research target of the present UV package for the OLED is to seek the UV glue with the lower permeability of the water vapor. This demands that the accumulation of the UV glue organic molecules gets more compacted after curing. Accordingly, the permeating path of the water vapor among the molecules becomes narrower. The permeability of the water vapor gets smaller.
Frit package technology is a new type panel glass package skill under development now. In China, almost no related documents are published. It is to mix the glass powder to be a solution with a certain viscosity. The solution is coated on the package glass and heated to remove the solvent. Then, after the glasses to be package have been attached, the laser is activated to burn and melt the frit glass powder instantly. Ultimately, the two sheet glasses are attached and bonded together. The Frit skill uses the inorganic package media. Therefore, the capability of resisting water vapor and oxygen is so strong. For now, the skill patents of the frit package are monopolized by only few foreign companies.
Mostly, the present UV package method of OLED is merely coating the UV glue on the surface of the package cover plate, and then, the package cover plate is oppositely attached to the TFT substrate. With the UV light irradiation, the UV glue is solidified. Thereby, the package of the TFT substrate with the package cover plate is accomplished. However, the OLED element on the TFT substrate is highly sensitive to the water vapor and the oxygen. The capability of the present UV package method to resist the water vapor and the oxygen is so poor that the arrangement of the dryer is required to reduce the water vapor that pass through the UV glue and reaches to the inside of the sealed space and to extends the usage lifetime of the OLED element. Nevertheless, the present UV package method only can be applicable to the bottom emitting OLED element structure. The package result of the Frit package good but the process is complicated and the equipment is amazingly expensive.